The present invention relates to a high density ceramic thick film fabrication method by screen printing and particularly, to a high-density ceramic thick film fabrication method by screen printing having advantages that patterning is not needed to fabricate a ceramic thick film and thick films of a preferred pattern size can be formed directly.
In case of fabricating a ceramic thick film by screen printing, there is a main problem that it is difficult to densify a film. Conventionally, a ceramic thick film by screen printing has been densified by adding glassy phase which can be easily fused in a heat processing and filled among particles in a paste for screen printing process. Another method for densification of the film is to perform a pressurized heat process.
Pb (Zr,Ti)O3(PZT) has been studied for applying to micro devices since the ceramic material has piezoelectric and pyroelectric properties. Koch et al. studied a thick film fabrication method by adding 5% of lead borosilicate glass to a paste [Sensors and Actuators A, 70 (1998)98-103]. Chen et al. conducted researches for achieving two objects of densifying and low temperature firing [J. of Appl. Phys, 77(1995)3349-33531] forming a glassy phase by adding 4% of Li2 CO3 and Bi2 O3. In addition, Yao et al. conducted a research for densifying a PZT thick film on an alumina substrate by isostatic pressing after screen printing [Sensros and Actuators A, 71 (1998) 139-143]. However, in this method heat processing temperature was so high as 1130xc2x0 C. that the method could not be applied for micro device element formed on Si.
As another trial for densifing a film, Barrow et al. used a ceramic powders mixed with a sol made of same material. Since empty spaces among ceramic particles were filled with the sol, a denser thick film can be fabricated. They formed a thick film using PZT powders mixed with PZT sol to deposit a 20 xcexcm of film at low temperature as 650xc2x0 C. [Appl. Phys. 8(1997) 876-881]. However, the above method has disadvantages that after depositing a film, a post-processing of patterning a film using a mask and etching the film should be required and that forming a uniform film is limited due to separation of ceramic sol and ceramic particles while the film is coated.
Therefore, an object of the present invention is to provide a method for fabricating a ceramic thick film at low temperature with the conventional printing method solving the problem of complexity of the conventional art which needs additional patterning processing.
The present invention provides a high density ceramic thick film fabrication method by screen printing which is comprised the steps of providing vehicle comprising an organic binder and solvent, dispersing ceramic powders into the vehicle to be paste, forming the paste to thick film by screen printing, removing the organic binder from the film, applying sol or sol-like solution to the surface of the film so that the sol or sol-like solution can infiltrate into the film, removing remaining sol or sol-like solution from the surface of the film, drying and preheating the film and sintering the film.